U.S. patent application number 12/519586 was filed with the patent office on 2009-12-24 for induction heating appliance for cooking.
Invention is credited to Kazuichi Okada, Masahiro Yokono.
Application Number | 20090314771 12/519586 |
Document ID | / |
Family ID | 39536303 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090314771 |
Kind Code |
A1 |
Okada; Kazuichi ; et
al. |
December 24, 2009 |
INDUCTION HEATING APPLIANCE FOR COOKING
Abstract
An infrared sensor for detecting infrared rays of light and a
light emitting element are disposed below a light transmittable top
plate, which has a hearing area for heating an article to be heated
placed thereon, in juxtaposed fashion relative to each other, so
that infrared rays of light radiated from the article to be heated
may be guided towards the infrared sensor. A light guide portion is
provided for guiding rays of flight, emitted from the light
emitting element, towards a heating area of the top plate, and the
rays of light emitted from the light emitting element and guided by
the light guide portion are projected onto the top plate through an
upper opening of the light guide portion so that such rays of light
can be noticed with eyes within the heating area.
Inventors: |
Okada; Kazuichi; (Hyogo,
JP) ; Yokono; Masahiro; (Hyogo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK L.L.P.
1030 15th Street, N.W., Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
39536303 |
Appl. No.: |
12/519586 |
Filed: |
December 18, 2007 |
PCT Filed: |
December 18, 2007 |
PCT NO: |
PCT/JP2007/074297 |
371 Date: |
June 17, 2009 |
Current U.S.
Class: |
219/647 ;
219/660 |
Current CPC
Class: |
H05B 2213/07 20130101;
H05B 6/062 20130101 |
Class at
Publication: |
219/647 ;
219/660 |
International
Class: |
H05B 6/06 20060101
H05B006/06; H05B 6/12 20060101 H05B006/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2006 |
JP |
2006-339593 |
Claims
1-11. (canceled)
12. An induction heating appliance for cooking which comprises: a
body; a light transmittable top plate provided atop the body and
having a heating area for heating an article to be heated with the
latter placed thereon; a heating coil disposed below the top plate
in face-to-face relation with the heating area for generating
magnetic fields necessary to induction heat the article to be
heated; an infrared sensor disposed below the top plate for
detecting infrared rays of light; a light emitting element disposed
below the top plate; a light guide portion for guiding the infrared
rays of light, emitted from the article to be heated, towards the
infrared sensor; and a control means for controlling an output of
the heating coil based on an output signal from the infrared
sensor, wherein the top plate is provided with an infrared incident
region positioned immediately above an upper opening of the light
guide portion to guide the infrared rays of light, emitted from the
article to be heated, towards the light guide portion, and the
infrared incident region is also positioned at a location inwardly
of an outer periphery of the heating coil and on a straight line
extending in a forward and rearward direction of the body and
passing across a center of the heating coil, when viewed from above
the body, or its proximity and offset forwardly from the center of
the heating coil, so that rays of light emanating from the light
emitting element are emitted within the infrared incident region to
allow the rays of light to be noticed within the heating area when
viewed from above the body.
13. The induction heating appliance for cooking as claimed in claim
12, wherein in pace of the arrangement, in which the light emitted
from the light emitting element is caused to illuminate within the
infrared incident region and such light is noticeable within the
heating area when viewed from above the body, the light emitted
from the light emitting element is caused to illuminate in
proximity to the infrared incident region and such light is
noticeable within the heating area when viewed from above the
body.
14. The induction heating appliance for cooking as claimed in claim
12, wherein the infrared incident region is provided only at one
location inwardly of the outer periphery of the heating coil.
15. An induction heating appliance for cooking which comprises: a
body; a light transmittable top plate provided atop the body and
having a heating area for heating an article to be heated with the
latter placed thereon; a heating coil disposed below the top plate
in face-to-face relation with the heating area for generating
magnetic fields necessary to induction heat the article to be
heated; an infrared sensor disposed below the top plate for
detecting infrared rays of light; a light emitting element disposed
below the top plate; a light guide portion for guiding the infrared
rays of light, emitted from the article to be heated, towards the
infrared sensor; and a control means for controlling an output of
the heating coil based on an output signal from the infrared
sensor, wherein the top plate is provided with an infrared incident
region positioned at a location inwardly of an outer periphery of
the heating coil and offset from a center of the heating coil to
guide the infrared rays of light, emitted from the article to be
heated, towards the light guide portion, so that rays of light
emanating from the light emitting element are emitted within the
infrared incident region to allow the rays of light to be noticed
within the heating area when viewed from above the body, and
wherein the light guide portion guides the light, emitted from the
light emitting element, towards the infrared incident region, and
the infrared incident region is partly or entirely noticeable when
the light emitted from the light emitting element and guided within
the light guide portion is projected towards the top plate through
an opening of the light guide portion.
16. The induction heating appliance for cooking as claimed in claim
12, wherein when viewed from above the body, the infrared incident
region has a center arranged on a straight line passing across a
center of the heating coil and a center of a light emitting
portion, which is a region where the light emitted from the light
emitting element can be noticed, or its vicinity and between the
center of the heating coil and the center of the light emitting
portion.
17. The induction heating appliance for cooking as claimed in claim
16, wherein there is further provided a light guide element, upon
which the light from the light emitting element is incident and
which has a light emitting surface illuminated in an annular shape,
and the light from the light emitting element is guided from the
light emitting surface of the light emitting element towards the
light guide portion.
18. The induction heating appliance for cooking as claimed in claim
17, wherein the infrared rays of light radiated from the article to
be heated is guided towards the infrared sensor through the opening
after having passed through a through-hole formed inside the light
emitting surface.
19. The induction heating appliance for cooking as claimed in claim
16, wherein the infrared sensor and the light emitting element
altogether form a sensor unit, and the sensor unit includes a
printed circuit board for fixing and electrically connecting the
infrared sensor and the light emitting element, a housing made of
an electroconductive metallic material and accommodating therein
the printed circuit board, and wherein the housing has a lower
extension tube extending towards the infrared sensor and the light
emitting element, with the infrared sensor and the light emitting
element being accommodated within the lower extension tube.
20. The induction heating appliance for cooking as claimed in claim
19, further comprising a light diffusing ring having a through-hole
above the infrared sensor and the light emitting element, wherein
the infrared sensor is arranged below the through-hole.
21. An induction heating appliance for cooking which comprises: a
body; a light transmittable top plate provided atop the body and
having a heating area for heating an article to be heated with the
latter placed thereon; a heating coil disposed below the top plate
in face-to-face relation with the heating area for generating
magnetic fields necessary to induction heat the article to be
heated; an infrared sensor disposed below the top plate for
detecting infrared rays of light; a light emitting element disposed
below the top plate; a light guide portion for guiding the infrared
rays of light, emitted from the article to be heated, towards the
infrared sensor; and a control means for controlling an output of
the heating coil based on an output signal from the infrared
sensor, wherein the top plate is provided with an infrared incident
region positioned immediately above an upper opening of the light
guide portion at a location inwardly of an outer periphery of the
heating coil and offset from the center of the heating coil to
guide the infrared rays of light, emitted from the article to be
heated, towards the light guide portion, so that rays of light
emanating from the light emitting element are emitted in proximity
to the infrared incident region to allow the rays of light to be
noticed within the heating area when viewed from above the body,
and wherein there is further provided a second light guide portion
separated from the light guide portion by a light shielding wall,
and the light emitted from the light emitting element travels
through the second light guide portion to illuminate a light
diffusing layer formed in proximity to the infrared incident
region.
22. An induction heating appliance for cooling which comprises: a
body; a light transmittable top plate provided atop the body and
having a heating area for heating an article to be heated with the
latter placed thereon; a heating coil disposed below the top plate
in face-to-face relation with the heating area for generating
magnetic fields necessary to induction heat the article to be
heated; an infrared sensor disposed below the top plate for
detecting infrared rays of light; a light emitting element disposed
below the top plate; a light guide portion for guiding the infrared
rays of light, emitted from the article to be heated, towards the
infrared sensor; and a control means for controlling an output of
the heating coil based on an output signal from the infrared
sensor, wherein the top plate is provided with an infrared incident
region positioned immediately above an upper opening of the light
guide portion at a location inwardly of an outer periphery of the
heating coil and offset from the center of the heating coil to
guide the infrared rays of light, emitted from the article to be
heated, towards the light guide portion, so that rays of light
emanating from the light emitting element are emitted within or in
proximity to the infrared incident region to allow the rays of
light to be noticed within the heating area when viewed from above
the body, and wherein the infrared incident region is arranged,
when viewed from above the body, on a straight line passing across
the center of the heating coil and a center of the light emitting
portion, which is a region at which the rays of light emitted from
the light emitting element are noticeable, or its vicinity and
between the center of the heating coil and the center of the light
emitting portion.
23. The induction heating appliance for cooking as claimed in claim
13, wherein the infrared incident region is provided only at one
location inwardly of the outer periphery of the heating coil.
24. The induction heating appliance for cooking as claimed in claim
13, wherein when viewed from above the body, the infrared incident
region has a center arranged on a straight line passing across a
center of the heating coil and a center of a light emitting
portion, which is a region where the light emitted from the light
emitting element can be noticed, or its vicinity and between the
center of the heating coil and the center of the light emitting
portion.
Description
TECHNICAL FIELD
[0001] The present invention relates to an induction heating
appliance for induction heating a material to be heated, which
utilizes an infrared sensor for controlling the temperature of the
material to be heated.
BACKGROUND ART
[0002] The prior art induction heating appliance for cooking is so
designed that an infrared sensor is arranged at a center of a
heating coil and an inverter circuit is controlled by a controlling
means in dependence on an output from the infrared sensor to
thereby control the output of the heating coil. (See, for example,
Patent Document 1 listed below.)
[0003] Patent Document Japanese Laid-open Patent Publication No.
2005-38660
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0004] It has, however, been found that in the induction heating
appliance for cooking of the structure referred to above, when an
article to be heated such as, for example, a pot, which is empty
(nothing to be cooked is contained in the article to be heated),
temperature abruptly increases at a portion of the article to be
heated above that portion of the heating coil winding intermediate
between the outermost periphery thereof and the innermost periphery
thereof, where the density of magnetic flux developed is highest to
emit the maximum heat during the heating, and, therefore, it often
occurs that as a result of delay in response to control the heating
output with respect to a high temperature region of the article to
be heated, when a thin-walled stainless steel pot of a kind having
an inferior thermal conductivity and a low heat capacity is used as
the article to be heated, the bottom of the pan tends to be red
heated enough to deform by the effect of the elevated temperature
or a material to be cooked containing a slight quantity of oil or
the like will be heated to a high temperature.
[0005] If the infrared sensor is arranged so as to detect the
temperature of the article to be heated which is placed at an
intermediate portion of the heating coil, not the center of the
heating coil, or in the vicinity of the inner periphery of the
winding of the heating coil, the above discussed problems would be
resolved. However, where the infrared sensor is to be provided
below the top plate, an incident window (hereinafter referred to as
an infrared incident region), through which infrared rays of light
from the article to be heated that is placed on the top plate, can
be incident upon the infrared sensor, the infrared sensor will be
disposed at a location offset from the center of the heating coil.
In such case, the article to be heated will not be necessarily
placed above the infrared incident region and, if the user
erroneously places the article to be heated not to obstruct the
infrared incident region, the infrared sensor will fail to detect
the temperature of the article to be heated properly. In
particular, in the case where the ambiance around the induction
heating appliance for cooking is dark, a problem is often
recognized that the infrared incident region is hardly noticed with
eyes.
[0006] The present invention has been devised with due
consideration paid to those problems inherent in the prior art and
has for its object to provide a convenient induction heating
appliance for cooking, in which the incident region, where infrared
rays of light emitted from the article to be heated can be incident
on the infrared sensor, can be easily noticed with eyes so that the
control of the temperature of the article to be heated in
dependence on the infrared sensor can be accomplished
assuredly.
Means to Solve the Problems
[0007] In accomplishing the above object, the induction heating
appliance for cooking according to the present invention includes a
light transmittable top plate provided atop a body and having a
heating area for heating an article to be heated with the latter
placed thereon; a heating coil disposed below the top plate in
face-to-face relation with the heating area for generating magnetic
fields necessary to induction heat an article to be heated; an
infrared sensor disposed below the top plate for detecting infrared
rays of light; a light emitting element disposed below the top
plate; a light guide portion for guiding the infrared rays of
light, emitted from the article to be heated, towards the infrared
sensor; and a control means for controlling an output of the
heating coil based on an output signal from the infrared sensor,
characterized in that an infrared incident region for guiding the
infrared rays of light, emitted from the article to be heated,
towards the light guide portion is provided at a location inwardly
of an outer periphery of the heating coil of the top plate and
offset from a center of the heating coil, so that rays of light
emanating from the light emitting element are emitted within the
infrared incident region to allow the rays of light to be noticed
within the heating area when viewed from above the body.
[0008] In pace of the arrangement, in which the light emitted from
the light emitting element is caused to illuminate within the
infrared incident region and such light is noticeable within the
heating area when viewed from above the body, the light emitted
from the light emitting element may be caused to illuminate in
proximity to the infrared incident region and such light is
noticeable within the heating area when viewed from above the
body.
[0009] The infrared incident region is provided only at one
location inwardly of an outer periphery of the heating coil and may
be arranged on a straight line, which extends across a center of
the heating coil when viewed from above the body, in a direction
forwards and rearwards or in proximity thereto and forwardly of the
center of the heating coil.
[0010] The light guide portion may guide the light, emitted from
the light emitting element, towards the infrared incident region,
and the infrared incident region may be partly or entirely
noticeable when the light emitted from the light emitting element
and guided within the light guide portion is projected towards the
top plate through an opening of the light guide portion.
[0011] When viewed from above the body, the infrared incident
region may have a center arranged on a straight line passing across
a center of the heating coil and a center of a light emitting
portion, which is a region where the light emitted from the light
emitting element can be noticed, or its vicinity and between the
center of the heating coil and the center of the light emitting
portion.
[0012] A light guide element, upon which the light from the light
emitting element is incident and which has a light emitting surface
illuminated in an annular shape may be further provided, in which
case the light from the light emitting element is guided from the
light emitting surface of the light emitting element towards the
light guide portion.
[0013] The infrared rays of light radiated from the article to be
heated may be guided towards the infrared sensor through the
opening after having passed through a through-hole formed inside
the light emitting surface.
[0014] The infrared sensor and the light emitting element
altogether may form a sensor unit, in which case the sensor unit
includes a printed circuit board for fixing and electrically
connecting the infrared sensor and the light emitting element, a
housing made of an electroconductive metallic material and
accommodating therein the printed circuit board. The housing has a
lower extension tube extending towards the infrared sensor and the
light emitting element, with the infrared sensor and the light
emitting element being accommodated within the lower extension
tube. In this case, a light diffusing ring having a through-hole
above the infrared sensor and the light emitting element may be
further provided, and the infrared sensor is arranged below the
through-hole.
[0015] There may be provided a second light guide portion separated
from the light guide portion by a light shielding wall, in which
case the light emitted from the light emitting element travels
through the second light guide portion to illuminate in proximity
to the infrared incident region.
[0016] The infrared incident region may be arranged, when viewed
from above the body, on a straight line passing across a center of
the heating coil and a center of the light emitting portion, which
is a region at which the rays of light emitted from the light
emitting element is noticeable, or its vicinity and between the
center of the heating coil and the center of the light emitting
portion.
EFFECTS OF THE INVENTION
[0017] According to the present invention, since the infrared
sensor and the light emitting element are provided below the top
plate, and the rays of light emanating from this light emitting
element are projected onto the top plate to enable the infrared
incident region, which is defined in a part of the heating area, or
its proximity to be noticed with eyes, if the user places the
article to be heated on the infrared incident region, which forms a
light emitting portion then noticed, or the infrared incident
region formed in the vicinity of the light emitting portion, the
infrared rays of light emanating from a bottom surface of the
article to be heated can be efficiently and assuredly guided
towards the infrared sensor, so that the temperature of the article
to be heated can be controlled through the infrared sensor. Also,
even when the ambiance around the induction heating appliance for
cooking is dark, the infrared incident region can easily be noticed
with eyes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an exploded perspective view of an induction
heating appliance for cooking according to the present
invention;
[0019] FIG. 2 is an exploded perspective view showing one of
heating coils and its proximity provided in the induction heating
appliance for cooking shown in FIG. 1;
[0020] FIG. 3 is a block diagram showing a control circuit for the
heating coil;
[0021] FIG. 4 is a sectional view of a sensor unit provided in the
induction heating appliance for cooking shown in FIG. 1;
[0022] FIG. 5 is a sectional view showing a modified form of the
sensor unit shown in FIG. 4;
[0023] FIG. 6 is a sectional view showing another modified form of
the sensor unit shown in FIG. 4;
[0024] FIG. 7 is a sectional view showing a further modified form
of the sensor unit shown in FIG. 4;
[0025] FIG. 8 is a sectional view showing a still further modified
form of the sensor unit shown in FIG. 4;
[0026] FIG. 9 is an exploded perspective view of the induction
heating appliance for cooking, which is provided with the sensor
unit shown in FIG. 8;
[0027] FIG. 10 is a sectional view showing a yet further modified
form of the sensor unit shown in FIG. 4;
[0028] FIG. 11 is an exploded perspective view showing the heating
coil, which is provided with the sensor unit shown in FIG. 10, and
its proximity;
[0029] FIG. 12 is a block diagram showing the control circuit
applicable where the sensor unit shown in FIG. 8 or FIG. 10 is
employed;
[0030] FIG. 13A is a front elevational view in the case where a
light diffusing layer is formed in a light emitting region provided
in a top plate of the induction heating appliance for cooking;
[0031] FIG. 13B is a front elevational view in the case where
another light diffusing layer is formed in the light emitting
region provided in the top plate of the induction heating appliance
for cooking;
[0032] FIG. 13C is a front elevational view in the case where a
further light diffusing layer is formed in the light emitting
region provided in the top plate of the induction heating appliance
for cooking;
[0033] FIG. 13D is a front elevational view in the case where a
still further light diffusing layer is formed in the light emitting
region provided in the top plate of the induction heating appliance
for cooking; and
[0034] FIG. 13E is a front elevational view in the case where a yet
further light diffusing layer is formed in the light emitting
region provided in the top plate of the induction heating appliance
for cooking.
EXPLANATION OF REFERENCE NUMERALS
TABLE-US-00001 [0035] 2: Body 4: Top unit 4a: Top plate 4b: Frame
4c: Front edge 6: First heating coil 8: Second heating coil 8a:
Inner coil 8b: Outer coil 8c: Gap 8d: Outer periphery 8e: Center
10: Radiant heater 12: Roaster heating chamber 14: Roaster door 16:
Operating console 18: First printed substrate 20: Second printed
substrate 22: Cooling fan 24: Air intake duct 26: Air intake port
28: Exhaust port 30: Flange 32: Heat shielding partition wall 34:
Support spring 35: Heating area 35a: Infrared incident region 35b:
Light emitting region 35c: Printed film 35d: Light absorbing film
35e: Center 36: Heating coil support base 36a: Light guide portion
36b: Recess 36c: Lower opening 36d: Upper opening 36e: Partition
wall 36f: Exit port 36g: Mount 36h: Second light guide element 36i:
Step 36j: Center 37: Ferrite 38: Thermistor 38a: Thermistor holder
40: Infrared sensor 41: Convex lens 42: Temperature detecting means
44: Control means 46: Inverter circuit 48, 48A, 48B, 48C, 48D, 48E:
Sensor unit 50: Unit housing 50a: Shielding portion 52: Printed
circuit board 54: Light emitting element 56: Connecting cable 58:
Connector 59: Sensor covering 60: Light guide tube (light guide
portion) 60a: Upper opening 60b: Lower opening 60c: Lower extension
tube 60d: Second light guide tube (second light guide portion) 62:
Screw member 67: Light guide element 67b: Light emitting portion
67c: Center 68: Light guide element 68a: Through-hole 68b: Bent
portion 70: Light diffusing ring 70a: Through-hole 72: Light sensor
73: Illuminance detecting means 74: Partition wall 76: Light
diffusing layer 78: Transparent portion 80: Colored light
transmittable layer A: Article to be heated C, C1: Induction
heating appliance for cooking X: Transverse center line Y:
Longitudinal center line
BEST MODE FOR CARRYING OUT THE INVENTION
[0036] Preferred embodiments of the present invention will be
described hereinafter with reference to the accompanying
drawings.
[0037] FIG. 1 illustrates an induction heating appliance C for
cooking according to the present invention, which is provided with
a body 2, a top unit 4 including a light transmittable top plate
4a, made of a crystallized ceramic material and fitted to the top
of the body 2, and a metallic frame 4b disposed around the
periphery of the top plate 4a, first and second heating coils 6 and
8 arranged below a front portion of the top plate 4a, and a radiant
heater 10 arranged rearwardly thereof. Also, a roaster heating
chamber 12 is provided below the second heating coil 8 positioned
on a left side when the body 2 is viewed from front and is
selectively opened and closed by a roaster door 14 pivotally fitted
to a front surface thereof. A tray (not shown), a grill (not shown)
and heaters (not shown) disposed above and below the grill are
accommodated within the roaster heating chamber 12, rendering the
latter to form a double sided heating roaster.
[0038] Also, an operating console 16, through which the output of
the above described heating means can be set, is provided on a
right side of the front surface of the body 2 and a first printed
substrate 18, forming a drive circuit for the first heating coil 6,
and a second printed substrate 20 forming a drive circuit for the
second heating coil 8 are provided rearwardly thereof and
positioned one above the other. A scirocco type cooling fan 22,
having a rotary shaft lying in a direction perpendicular to the
printed substrates 18 and 20, and a motor (not shown) for driving
the cooling fan 22 are provided at a position rearwardly of and
proximate to the two printed substrates 18 and 20, and the cooling
fan 22 and the motor are enclosed by an air intake duct 24. It is
to be noted that respective drive circuits for the radiant heater
10 and a roaster heater are formed inside the printed substrates 18
and 20.
[0039] Also, an air intake opening 26, communicated with the air
intake duct 24, and an exhaust opening 28 adjoining the air intake
opening 26 and on the side adjacent the roaster heating chamber 12
are formed in a rear portion of a top surface of the body 2.
[0040] As shown in FIG. 1, the body 2 has an integrally formed
outer shell or framework and is of a built-in type capable of being
supported in a kitchen by means of a top flange 30 of the outer
shell. Only a structure having lax temperature limitations and hard
to be thermally damaged, such as including a heat shielding
partition wall 32, support springs 34 for the second heating coil
8, a junction terminal block (not shown) for electrically
connecting the second heating coil 2 with the second printed
substrate 20 and others, is arranged above the roaster heating
chamber 12. In addition, when the body 2 is viewed from top, the
cooling fan 22, the first printed substrate 18 and the second
printed substrate 20 are arranged at a position not overlapping the
roaster heating chamber 12 and laterally thereof.
[0041] When the induction heating appliance C for cooking of the
construction described above in accordance with the present
invention is to be used, after an article to be heated A (See FIG.
3.) has been placed on the top plate 4a at a location above an
arbitrarily chosen one of the heating means including the first
heating coil 6, the second heating coil 8 and the radiant heater
10, or a material to be cooked has been loaded into the roaster
heating chamber 12, the operating console 16 has to be manipulated
to initiate a desired cooking. In order to provide a visual
indication of the site where the article to be heated A has to be
placed, a heating area 35, where the article to be heated A is
placed, is displayed so as to encompass a portion of the top plate
4a aligned with each of the heating means 6, 8 and 10, which area
35 is defined by a respective round film 35c printed on a rear
surface (an undersurface) of the top plate 4a. It is to be noted
that the heating area may not be limited to a round shape and may
not be necessarily matched with the shape of that portion of the
top plate 4a encompassed by the respective heating means 6, 8 and
10 and may be satisfactory provided that it serves the purpose of
providing a visual indication of the position of the respective
heating means. Also, the printed film 35c used to display the
heating area 35 has its outer side (an undersurface) formed with a
black colored light absorbing film 35d, having a substantially zero
light transmittance, by means of a printing technique. It is to be
noted that the printed film 35c indicative of the heating area 35
may be formed on a front surface, not the rear surface, of the top
plate 4a. Also, the printed film 35c may be in the form of a line
of film.
[0042] During the use of the induction heating appliance C for
cooking, the internal temperature inside the body 2 elevates, but
by the effect of the cooling fan 22, the ambient air is sucked into
the body 2 through the air intake opening 26 and the sucked air
then flows within a space above the printed substrates 18 and 20
and are finally discharged through the exhaust opening 28 by way of
a space on the side of the roaster heating chamber 12 within the
body 2. As a result thereof, a heating portion within the body 2,
including the heating means 6, 8 and 10, is cooled with the
temperature thereof decreased consequently.
[0043] Hereinafter, of control systems of the induction heating
appliance C for cooking, particularly with respect to the
respective control systems for the first and second heating coils 6
and 8, reference will be made to the second heating coil 8 by way
of example.
[0044] FIG. 2 illustrates the second heating coil 8 and its
surroundings, and the second heating coil 8 has a split winding
structure made up of an inner coil 8a and an outer coil 8b and is
retained on a heating coil support base 36 made of a resinous
material having a low infrared transmittance. Also, a ferrite 37
(See FIG. 3.) for concentrating magnetic flux, emanating from the
second heating coil 8 towards a rear surface thereof, in the
vicinity of the second heating coil 8 is fitted to an undersurface
of the heating coil support base 36, and a cylindrical light guide
portion 36a for guiding infrared rays of light emitted from a
bottom portion of the article to be heated A (See FIG. 3.) so as to
be incident upon an infrared sensor as will be described later, or
light emitted from a light emitting element as will be described is
formed in a gap 8c delimited between the inner coil 8a and the
outer coil 8b. Further, in the vicinity of a center of the second
heating coil 8, a thermistor 38 for detecting the temperature of
the bottom surface of the article to be heated A is engaged in and
supported by a groove of a thermistor holder 38a, made of a heat
resistant synthetic resin, and is fitted to the top plate 4a after
having been urged by a spring (not shown) to contact the top plate
4a.
[0045] It is to be noted that the infrared sensor referred to above
is provided for detecting the temperature of the article to be
heated A in a manner similar to the thermistor 38, but is excellent
in temperature response as compared with that of the thermistor 38,
and regarding control circuits for the first heating coil 6 and the
second heating coil 8 that are controlled in dependence on an
output of this infrared sensor, the second heating coil 8 by way of
example will be hereinafter described with particular reference to
FIG. 3.
[0046] As shown in FIG. 3, in order for the infrared sensor 40 to
be less susceptible to influences which would be brought about by
magnetic flux from the second heating coil 8, the infrared sensor
40 is disposed below the ferrite 37 defining a magnetic path for
shielding magnetic flux oriented downwardly from the second heating
coil 8 and, also, below a lower open end 36c of the cylindrical
light guide portion 36a formed integrally with the heating coil
support base 36. A convex lens 41 is disposed as a light converging
means on the path of travel of infrared rays of flight emitted from
the bottom surface of the article to be heated A so as to travel
towards the infrared sensor 40, so that the infrared rays of flight
emitted from the article to be heated A can be collected. An output
from the infrared sensor 40 is supplied to a temperature detecting
means 42, and the temperature of the article to be heated A is then
detected by the temperature detecting means 42. An output from the
temperature detecting means 42 is supplied to a control means 44,
and the control means 44 then controls an output of an inverter
circuit 46 for supplying a high frequency current to the second
heating coil 8 in response to the signal from the temperature
detecting means 42.
[0047] The heating operation performed by the second heating coil 8
of the structure as hereinbefore described will be described
hereinafter.
[0048] Assuming that the heating is initiated, the inverter circuit
46 supplies a high frequency current of a frequency equal to or
higher than 20 kHz to the second heating coil 8 so that the article
to be heated A can be self-heated by the effect of an eddy current
induced by magnetic flux (magnetic fields) emanating from the
heating coil 8. The temperature of the bottom of the article to be
heated A at a transit time subsequent to the start of the heating
is such that under the influence of a distribution of densities of
magnetic flux from the second heating coil 8, an area adjacent an
inner edge of the outer coil 8b attains a temperature higher than
that of a substantial center of the second heating coil 8.
Accordingly, in order to detect the temperature at a high
temperature area of the article to be heated A, the infrared sensor
40 is disposed below the gap 8c delimited between the inner coil 8a
and the outer coil 8b of the second heating coil 8; a detection
output from the infrared sensor 40 is outputted to the control
means 44 after having been converted by the temperature detecting
means 42 into a detected temperature; and if the detected
temperature exceeds a predetermined temperature or if the gradient
of the detected temperature exceeds a predetermined value, the
inverter circuit 46 is controlled by the control means 44 so as to
reduce the output thereof.
[0049] In the present invention, the infrared sensor 40 is formed
as a sensor unit having a light emitting element arranged in the
vicinity thereof, and the construction of the sensor unit will now
be described with particular reference to FIG. 4.
[0050] As shown in FIG. 4, the sensor unit 48 is arranged below the
heating coil support base 36 and this sensor unit 48 includes a
unit housing 50, made of an electroconductive metallic material
such as, for example, aluminum or brass, and a printed circuit
board 52 accommodated within the unit housing 50. The infrared
sensor 40 and the convex lens 41, and a light emitting element 54
such as, for example, an LED are fixed on the printed circuit board
52, and a connector 58 for electrically connecting those elements
and a cable 56 together is provided on the printed circuit board
52. Also, an area around the infrared sensor 40 and a lower portion
of the convex lens 41, excluding an infrared incident surface above
the convex lens 41, upon which infrared rays of light emitted from
the article to be heated A are incident, is enclosed by a tubular
sensor covering 59 having a light shielding function, so that light
other than the infrared rays of light from the article to be heated
A can be prevented from entering the convex lens 41.
[0051] The unit housing 50 has a shielding portion 50a for
magnetically shielding the light emitting element 54 and the
infrared sensor 40 provided on one side of the printed circuit
board 52 adjacent the second heating coil 8, and a cylindrical
light guide tube 60 having an upper opening 60a, defined at an
upper end thereof, and a lower opening 60b defined at a lower end
is formed integrally with the shielding portion 50a so as to
protrude towards the heating area, with the convex lens 41 and the
infrared sensor 40 positioned immediately below the lower opening
60b of the light guide tube 60. Also, the light emitting element 54
is fixedly mounted on the printed circuit board 52 at a location
proximate to the infrared sensor 40 so that rays of light emitted
therefrom can be directed towards an inner wall of the light guide
tube 60.
[0052] Also, a round recess 36b is formed in an undersurface of the
light guide portion 36a of the heating coil support base 36, and
this round recess 36b has an inner diameter so chosen as to be
greater than the outer diameter of the light guide tube 60, and the
unit housing 50 is secured to the heating coil support base 36 at a
location proximate to the light guide portion 36a by means of a
screw member 62 in a condition in which the upper end of the light
guide tube 60 is received within the round recess 36b with an upper
end face of the light guide tube 60 tightly contacting an end face
of the round recess 36b. It is to be noted that the inner diameter
of the light guide portion 36a and the inner diameter of the light
guide tube 60 are so chosen as to be equal to each other and,
hence, the light guide portion 36a and the light guide tube 60 have
respective inner surfaces held in flush with each other.
[0053] Also, as hereinabove described, the top plate 4a has a round
placement area (heating area 35) for the support of the article to
be heated A thereon, which area is defined by the printed film 35c,
but a portion of the printed film 35c is formed with a round cutout
so as to leave an infrared incident region 35a. This infrared
incident region 35a is defined immediately above an upper opening
36d of the light guide portion 36a in the heating coil support base
36 so as to confront the upper opening 36d and, also, the upper
opening 60a of the light guide tube 60, and the light transmittance
of the infrared incident region 35a is so chosen to be higher than
the light transmittance of a portion (the printed film 35c)
peripheral to such infrared incident region 35a. It is to be noted
that this infrared incident region 35a is for the purpose of
allowing the infrared rays of light, emitted from a portion of the
bottom surface of the article to be heated A, which is aligned with
the infrared incident region 35a, to pass therethrough towards the
light guide portion 36a.
[0054] When a food material is put into the article to be heated A
and is then to be cooked with the induction heating appliance C for
cooking, and when an electric power switch (not shown) of the
induction heating appliance C for cooking is subsequently turned
on, the light emitting element 54 emits rays of light, which are in
turn guided, after having been reflected by the inner wall of the
light guide portion 60 and the inner wall of the light guide tube
36a, and are finally used to illuminate the infrared incident
region 35 of the top panel 4a through the upper opening 60a of the
light guide tube 60 and the upper opening 36d of the light guide
portion 36a. Accordingly, since the user can readily ascertain the
presence of the infrared incident region 35a then illuminated by
the light emitted from the light emitting element 54, the heating
operation is ready to start when an OFF key (not shown) in the
operating console 16 is manipulated. In the case where the second
heating coil 8 is to be used, placement of the article to be heated
A on the top panel 4a so as to cover the area illuminated by the
light makes it possible for the infrared sensor 40 to receive
assuredly and efficiently the infrared rays of light, emitted from
the bottom surface of the article to be heated A and, hence, the
temperature of the article to be heated A can be controlled by the
infrared sensor 40. Also, even when the ambiance around the
induction heating appliance C for cooking is dark, the infrared
incident region 35a can be readily noticed.
[0055] When the article to be heated A is heated by the second
heating coil 8, the infrared rays of light emitted from the bottom
of the article to be heated A are guided towards the light guide
portion 36a in the heating coil support base 36 through the
infrared incident region 35a of the top plate 4a and are then
guided towards the light guide tube 60 in the unit housing 50,
which is held in engagement with the lower opening 36c at the lower
end of the light guide portion 36a, before they are incident upon
the infrared sensor 40. In response to the incident infrared rays
of light, the infrared sensor 40 generates an output, which is
subsequently supplied to the temperature detecting means 42 and,
thus, the temperature of the article to be heated A can be
controlled in the manner described above.
[0056] As hereinabove described, since the outgoing light from the
light emitting element 54 is guided towards the top plate 4a
through the light guide tube 60 and then through the light guide
portion 36a and, on the other hand, the rays of light emanating
from the article to be heated A are guided towards the infrared
sensor 40 along the same path, but in a direction reverse to the
direction of travel of the outgoing light from the light emitting
element 54, that is, through the light guide portion 36a and then
through the light guide tube 60, the light guide tube 60 and the
light guide portion 36a function as light guiding means for guiding
in both directions. Also, since the light guide tube 60 and the
light guide portion 36a, which form the light guiding means, extend
from a location in the vicinity of a light receiving surface of the
infrared sensor 40 to an upper surface of the second heating coil
8, the structure is such that it will be hardly affected by
influences brought about by the infrared emission from component
parts peripheral to the infrared sensor 40 such as, for example,
the second heating coil 8.
[0057] While in the foregoing description, reference has been made
only to the second heating coil 8 for the purpose of brevity, a
similar description equally applies to the first heating coil 6
that is positioned and configured in a manner similar to the second
heating coil 8.
[0058] As hereinbefore described, since the infrared incident
region 35a for guiding the infrared rays of light emanating from
the article to be heated A towards the light guide portion 36a is
provided in that portion of the top plate 4a, which corresponds in
position to the center of the second heating coil 8 and inwardly of
the outer periphery of the second heating coil 8, so that the light
emitted from the light emitting element 54 can be illuminated
within the infrared incident region 35a to allow the latter to be
noticed within the heating area 35, the user, when he or she places
the article to be heated A on the top plate 4a so as to cover the
infrared incident region 35a then noticed as illuminated, can cause
the infrared rays of light from the bottom surface of the article
to be heated A to be efficiently and assuredly incident upon the
infrared sensor 40, with the temperature of the article to be
heated A consequently controlled by the infrared sensor 40. Also,
even when the ambience around the induction heating appliance C for
cooking is dark, the infrared incident region 35a can readily be
noticed.
[0059] It is to be noted that similar effects can be obtained even
when in place of the arrangement in which the light emitted from
the light emitting element 54 is emitted within the infrared
incident region 35a, as hereinbefore described, so that the light
can be viewed within the heating area 35 when viewed from above the
body 2, the light emitted from the light emitting element 54 is
caused to emit in the vicinity of the infrared incident area 35a so
that it can be noticed within the heating area 35 when viewed from
above the body as will be described later (See FIGS. 8 to 10.).
[0060] Also, since the infrared incident region 35a is provided
only at one location inwardly of the outer periphery 8d of the
second heating coil 8 and on a straight line, which passes through
the center 8e of the second hearing coil 8 (or the center 35e of
the heating area 35) and extends in a direction forwards and
rearwards of the body 2 or in the vicinity thereof, or forwardly of
the center 8e of the second heating coil 8 when viewed from above
the body 2, the user can readily cover the infrared incident region
35a with the bottom of the article to be heated A, and the infrared
sensor 40 and the light emitting element can be constructed
inexpensively as one unitary set. Also, since the infrared incident
area 35a is chosen to be forwardly of the center 8e of the second
heating coil 8, the user can readily ascertain from the position,
where he or she does a cooking work, whether or not the infrared
incident region 35a is covered by the article to be heated A. When
the user after having placed the article to be heated A on the
heating area 35 moves the article to be heated A from rear to
front, the infrared incident region 35a can easily be covered by
the bottom surface of the article to be heated A while he or she
watches the infrared incident region 35a. Conversely, when the
article to be heated A is moved from front to rear, the infrared
incident region 35a then covered up by the article to be heated A
from a visible condition can be brought to a visible condition,
allowing the user to notice the position of the infrared incident
region 35a.
[0061] Also, positioning of the infrared incident region 35a at
that location on a center line Y extending in a longitudinal
direction, which is a straight line extending in a direction
forwardly and rearwardly across the center 8e of the second heating
coil 8, and forwardly of the center 8e of the second heating coil 8
is effective to markedly increase the handling ability by which the
user's job of covering the infrared incident region 35a can be
facilitated.
[0062] The reason therefor will be discussed hereinafter. When the
article to be heated A is moved, a job of moving it in a direction
forwardly and rearwardly from a condition, in which the center 35e
of the heating area 35 and the center of the bottom surface of the
article to be heated A are aligned with each other, can be most
conveniently and steadily performed. In view of this, in a
condition in which the infrared incident region 35a is not covered
up by the bottom surface of the article to be heated A while the
center 8e of the second heating coil 8 (the center 35e of the
heating area 35) and the center of the bottom of the article to be
heated A are aligned with each other, as compared with the case of
the infrared incident region 35a being positioned at a location
spaced the same distance from the center 8e in a different
direction relative to the center 8e of the second heating coil 8,
pull of the article to be heated A forwardly results in the
infrared incident region 35a moving relatively so as to follow the
centerline passing across the center of the article to be heated A
and, accordingly, the infrared incident region 35a can be stably
covered up by the bottom surface of the article to be heated A.
Conversely, where the infrared incident region 35a is covered up by
the bottom surface of the article to be heated A while the center
8e of the second heating coil 8 and the center of the bottom of the
article to be heated A are aligned with each other, as compared
with the case of the infrared incident region 35a being positioned
at a location spaced the same distance from the center 8e in a
different direction relative to the center 8e of the second heating
coil 8, it is possible to cause the infrared incident region 35a to
appear at a position nearest to the user when the article to be
heated A is moved in a direction right rearwardly. In this way, by
moving the center of the article to be heated A forwardly or
rearwardly along the straight line extending in the forward and
rearward direction passing across the center 8e of the second
heating coil 8, the position of the infrared incident region 35a
can be ascertained in a most readily viewable condition, in the
case where the infrared incident region 35a is covered by the
article to be heated A, and it can be stably covered up in the case
where the infrared incident region 35a is not covered by the
article to be heated A, thus facilitating the handling ability. It
is to be noted that the center line X extending in a transverse
direction shown in FIG. 1 is a straight line passing across the
center 35e of the heating area 35 and parallel to a front surface
14a of the body 2 (or a front edge 4c of the top unit 4). The
center 35e of the heating area 35 occupies a position immediately
above the center 8e of the second heating coil 8.
[0063] Also, because the light guiding means (the light guide tube
60 and the light guide portion 36a) is provided for guiding the
infrared rays of light, radiating from the article to be heated A,
towards the infrared sensor 40 and also for guiding the light,
emitted from the light emitting element 54, towards the infrared
incident region 35a, and because the rays of light emitted from the
light emitting element 54 and then guided by the light guiding
means 60 and 36a are projected onto the top plate 4a through the
upper opening 36d of the light guide portion 36a, which is an
opening of the light guiding means 60 and 36a, to enable the
infrared incident region 35a to be partly or entirely viewable, the
infrared incident region 35a itself is designed to emit light and,
accordingly, the infrared incident region 35a can be assuredly
covered up by the article to be heated A. Also, since the outgoing
light from the light emitting element 54 is guided towards the top
plate 4a through the light guide tube 60 and then through the light
guide portion 36a and, on the other hand, the infrared rays of
light emanating from the article to be heated A are guided towards
the infrared sensor 40 along the same path, but in a direction
reverse to that described above, through the light guide portion
36a and then through the light guide tube 60, the light guide tube
60 and the light guide portion 36a function as the bidirectional
light guiding means, making it possible to provide a simplified and
space-saving construction. It is to be noted that where the light
from the light emitting element 54 will adversely affect the
detecting operation of the infrared sensor 40, it is recommended to
cease the detecting operation of the infrared sensor 40 during the
length of time the light emitting element 54 is active to emit the
light or, alternatively, to employ a wavelength region of the
infrared sensor 40 to be detected, which is different from the
wavelength of light from the light emitting element 54.
[0064] Also, since the sensor unit 48 is constructed with the
infrared sensor 40 and the light emitting element 54 and includes
the printed circuit board 52 for fixing and electrically connecting
the infrared sensor 40 and the light emitting element 54 and the
unit housing 50 made of the electroconductive metallic material and
accommodating therein the printed circuit board 52; since the unit
housing 50 has the shielding portion 50a for electromagnetically
shielding the infrared sensor 40 and the light emitting element 54
both provided on the side of the printed circuit board 52 adjacent
the second heating coil 8; and since the light guiding means (the
light guide tube 60 and the light guide portion 36a) is formed
integrally with the shielding portion 50a so as to protrude in a
direction towards the heating area 35, not only can the sensor unit
48 be assembled compact in size, but the assemblage can be also
facilitated, thus rendering the infrared sensor 40 and the light
emitting element 54 to be hardly affected by noises originating
from an inverter and the second heating coil 8.
[0065] FIG. 5 illustrates a modified form of the sensor unit 48
shown in FIG. 4, and the sensor unit 48A shown in FIG. 5 is not
provided with the light guide tube 60 of the sensor unit 48 shown
in FIG. 4. The light guide portion 36a is extended downwardly with
the lower opening 36c brought to a position close to the infrared
sensor 40. A step 36i is formed in the vicinity of the lower end of
the light guide portion 36a and, when the unit housing 50 is
threaded to the heating coil support base 36 by means of the screw
member 62, a mount 36g below the step 36i extends through a hole
50b, defined in the shielding portion 50a, with the light guide
portion 36a engaged consequently with the shielding portion 50a.
The inner wall of the light guide portion 36a is colored black so
that rays of light can be absorbed thereby. The convex lens 41 (the
light collecting means) is arranged on the path along which the
infrared rays of light are guided from the article to be heated A
towards the infrared sensor 40, so that the infrared rays of light
emanating from the article to be heated A and passing through the
infrared incident region 35a can be guided towards the infrared
sensor 40.
[0066] Since the inner wall of the light guide portion 36a is so
colored black as to absorb the light, the field of view of the
infrared sensor 40 is limited by the upper opening 36d. By this
construction, it is possible not only to simplify the construction,
but also to reduce the heat, which will be transmitted from the
second heating coil 8 and/or the article to be heated A to the
infrared sensor 40, when the light guide path for the travel of the
infrared rays of light therethrough is formed by a part of the
light guide portion 36a which is a resinous article.
[0067] Also, a rod-like light guide element 67 is inserted and
fixed to a portion of the inner wall of the light guide portion 36a
on one side offset towards the frontward direction. This light
guide element 67 has, at its lower end, an incident face 67a
opposed to the light emitting element 54 and also has, at its upper
end, a light emitting face 67b opposed to the infrared incident
region 35a in the top plate 4a.
[0068] Rays of light emerging outwardly from the light emitting
face 67b illuminate the infrared incident region 35a and,
accordingly, the user can notice such light within the infrared
incident region 35a. Thus, since when viewed from above the body 2,
the infrared incident region 35a is disposed on the straight line
passing across the center 8e of the second heating coil 8 and the
center of the light emitting face 67b of the light guide element,
which is a region where the rays of light emitted from the light
emitting element 54 can be viewable, or its proximity and between
the center 8e of the second heating coil 8 and an approximate
center of the light emitting face 67b, it is possible to assuredly
place the bottom surface of the article to be heated A above the
infrared incident region 35a when the bottom surface of the article
to be heated A is covered by a light emitting portion 67b. It is to
be noted that a light shielding coating, which is, for example,
black in color, may be applied to a lateral side face of the light
guide element 67 to avoid leakage of light therefrom.
[0069] FIG. 6 illustrates another modified form of the sensor unit
48 shown in FIG. 4, and the sensor unit 48B shown in FIG. 6 is of a
structure, in which a light guide element 68 is disposed above the
infrared sensor 40 and the light emitting element 54.
[0070] The light guide element 68 is formed in an annular shape
having its center formed with a round through-hole 68a, and a part
thereof is formed with a bent portion 68b so as to confront a light
emitting portion of the light emitting element 54. Rays of light
emerging from the light emitting element 54 are incident upon the
light guide element 68 from an end face of the bent portion 68b,
the light guide element 68 having the through-hole 68a defined at
the center thereof is illuminated in its entirety, and an annulus
of light exits towards the article to be heated A, with an upper
face of the light guide element 68 serving as a light emitting face
from which that annulus of light emerges outwardly. Also, the
infrared rays of light from the article to be heated A are incident
upon the infrared sensor 40 through the through-hole 68a of the
light guide element 68.
[0071] Since the foregoing construction is such that the light from
the light emitting element 54 is injected; the light guide element
68 capable of allowing the light to emerge outwardly in the form of
an annulus of light is further provided; and the annulus of light
guided from the light emitting face of the light guide element 68
towards the light guiding means (the light guide tube 60 and the
light guide portion 36a) exits so as to travel towards the article
to be heated A, some advantages can be obtained that the amount of
light used to illuminate the infrared incident region 35a can be
increased and that the infrared incident region 35a can be
uniformly illuminated.
[0072] Also, since the infrared rays of light radiated from the
article to be heated A are guided towards the infrared sensor 40
through the upper opening 36d of the light guide portion 36a and
then through the through-hole 68a defined inside the light emitting
face of the light emitting element 54, it is possible to avoid the
possibility that the collecting of the infrared rays of light from
the article to be heated A may be disturbed.
[0073] FIG. 7 illustrates a further modified form of the sensor
unit 48 shown in FIG. 4, and the sensor unit C shown in FIG. 7 is
of a structure, in which the light guide tube 60 in the unit
housing 50 is extended to a position adjacent the printed circuit
board 52 or its proximity, and the infrared sensor 40 and the light
emitting element 54, which are positioned in proximity to each
other, are accommodated within a lower extension tube 60c continued
from the light guide tube 60. Also, a light diffusing ring 70
having a round through-hole 70a is provided above the infrared
sensor 40 and the light emitting element 54, and the infrared
sensor 40 is disposed below the through-hole 70a while the light
emitting element 54 is disposed below a site other than the
through-hole 70a.
[0074] This construction is effective not only to prevent light
inside the appliance or external light leaking through a gap in the
unit housing 50 in the vicinity of, for example, the connector 58
from being incident upon the infrared sensor 40 to thereby increase
the light collecting property, but also to reduce the leakage of
the light emitted from the light emitting element 54 so that the
brightness of the exit light from the top plate 4a, which the user
can notice, can be increased, since the unit housing 50 includes
the lower extension tube 60c extending towards the printed circuit
board 52 with the infrared sensor 40 and the light emitting element
54 accommodated within the lower extension tube 60c. Also, since
the light diffusing ring 70 having the through-hole 70a is provided
above the infrared sensor 40 and the light emitting element 54, and
the infrared sensor 40 is disposed below the through-hole 70a, the
light emitted from the light emitting element 54 is in the form of
a planar light, not a pencil of light, with the uniformity
increased consequently.
[0075] FIG. 8 illustrates a still further modified form of the
sensor unit shown in FIG. 4, and the sensor unit 48D shown in FIG.
8 is of a structure, in which a light sensor 72 is disposed in the
vicinity of the infrared sensor 40, and a partition wall 74 for
separating both of the infrared sensor 40 and the light sensor 72
from the light emitting element 54 is formed integrally with the
unit housing 50. Also, the light guide portion 36a in the heating
coil support base 36 has its interior similarly formed integrally
with a partition wall 36e dividing the interior into two chambers,
and the light guide portion 36a has its upper end formed with an
upper opening 36d and an exit port 36f. The top plate 4 has its
rear surface printed with a colored printed film 35c, which is
colored in, for example, a silver color, and the light emitting
region 35b is not printed with any colored printed film 35c but is
formed with a light diffusing layer 76. The infrared incident
region 35a is not printed with any colored printed film 35c. Since
the infrared incident region 35a is formed with the printed film,
which is colored in black or dark brown color, but is capable of
transmitting infrared rays of light therethrough, for concealing
the interior from view, the user can recognize the infrared
incident region 35a as a black window if the colored printed film
35c is of a bright color such as, for example, a silver color.
[0076] FIG. 9 illustrates an induction heating appliance C1 for
cooking having the sensor unit 48D of the structure shown in FIG.
8, and the light guide portion 36a in the heating coil support base
36 and the light guide tube 60, both cooperating with each other to
form the light guiding means, have an overall outer sectional shape
representing a substantially elliptical shape and, at the same
time, a path (the light guide portion 36a) of travel of the
infrared rays of light incident on the infrared sensor 40 and a
path (a second light guide portion 36h) of travel of the light
emitted from the light emitting element 54, which are separated
from each other by the partition walls 36e and 74, have respective
horizontal sections representing a substantially round shape. The
respective horizontal sectional shapes of the light guide tube 60
and the second light guide tube 60d are identical with those of the
light guide portion 36a and the second light guide portion 36h.
When viewed from above the body 2, the infrared incident region 35a
and a light emitting region 35b are positioned at respective
locations displaced inwardly of the heating area 35, that is,
inwardly of the outermost periphery of the second heating coil 8
and forwardly along the direction forwards and rearwards from the
center 8e of the second heating coil 8 (which direction is, in the
illustrated instance, referred to as a direction perpendicular to
the front edge 4c of the top unit 4 or in a direction perpendicular
to the front surface 14a of the body 2) and, when viewed from front
of the body 2, the both are laterally juxtaposed relative to each
other in a direction leftwards and rightwards (in a transverse
direction). In other words, when viewed from above (in a top plan
representation), the infrared incident region 35a and the light
emitting region 35b are juxtaposed relative to each other on
respective sides of a longitudinal center line Y, which is a
straight line passing across the center of the second heating coil
8 (the center of the heating area 35) in the direction forwards and
rearwards (in the longitudinal direction). The transverse center
line X in FIG. 9 is a straight line extending across the center 35e
of the heating area 35 (the center 8e of the second heating coil 8
when viewed from above) and parallel to the front surface 14a of
the body 2, and the infrared incident region 35a and the light
emitting region 35b are laid parallel to the straight line X.
[0077] As hereinabove described, since the top plate 4a is formed
with the light emitting region 35b, corresponding to the path of
travel of the light emitted from the light emitting element 54, and
the infrared incident region 35a, corresponding to the path of
travel of the infrared rays of light to be incident upon the
infrared sensor 40, in a fashion close towards, but separated from
each other, not only can the field of view of the infrared sensor
40 be narrowed, but the light emitted from the light emitting
element 54 can be also efficiently guided towards the light
emitting region 35b. Also, influences which the exit light from the
light emitting element 54 may bring about on the infrared sensor 40
can be suppressed.
[0078] FIG. 10 illustrates a yet further modified form of the
sensor unit shown in FIG. 4, and the sensor unit 48E shown in FIG.
10 differs from the sensor unit 48D shown in FIG. 8 in that, as is
the case with the construction shown in FIG. 5, the light guide
portion 36a shown in FIG. 8 is extended downwardly with the lower
opening 36c positioned in proximity to the infrared sensor 40 and
that, as shown in FIG. 11, the light emitting region 35b and the
infrared incident region 35a are displaced from the center of the
second heating coil 8 in the direction forwards and rearwards (in
the longitudinal direction) and forwardly. The step 36i is formed
in the vicinity of the lower end of the light guide portion 36a.
When the unit housing 50 is threaded to the heating coil support
base 36 by means of the screw member 62, a mount 36g downwardly of
the step 36i is engaged with the shielding portion 50a. By this
construction, the path of travel of the infrared rays of light,
limiting the field of view of the infrared sensor 40, and the path
of travel of light emitted from the light emitting element 54 can
be formed in a single component part for simplification and, also,
the heat, which may be transmitted from the second heating coil 8
and the article to be heated A to the infrared sensor 40, can be
reduced. Also, a rod-like light guide element 67 is inserted and
fixed to a portion of the inner wall of the light guide portion 36a
on one side offset towards the frontward direction. This light
guide element 67 has, at its lower end, an incident face 67a
opposed to the light emitting element 54 and also has, at its upper
end, a light emitting face 67b opposed to the infrared incident
region 35a in the top plate 4a. Rays of light emerging outwardly
from the light emitting face 67b illuminate the infrared incident
region 35a and, accordingly, the user can notice such light within
the infrared incident region 35a.
[0079] FIG. 11 illustrates the second heating coil 8, which is
provided with the sensor unit E, and its proximity. Although in
FIG. 9, the light emitting region 35b and the infrared incident
region 35a have been shown and described as juxtaposed to each
other in the direction leftwards and rightwards (in the transverse
direction), as viewed from front, and have been displaced forwardly
from the center of the second heating coil 8 in the direction
forwards and rearwards (in the longitudinal direction), the article
to be heated A can cover the infrared incident region 35a and be
heated with an increased handling ability if the light emitting
region 35b is juxtaposed forwardly in the direction forwards and
rearwards (in the longitudinal direction) from the center of the
second heating coil 8 as shown in FIG. 11. In other words, the user
generally places the article to be heated A with the center of the
bottom surface thereof matched with the center 8e of the second
heating coil 8. Where in this condition the bottom diameter of the
article to be heated A is sufficiently large enough to permit the
bottom surface thereof to cover the infrared incident region 35a,
it is possible to allow the infrared incident region 35a to be
stably covered with the article to be heated A while the distance
from the position of the infrared incident region 35a to an end of
the bottom surface of the article to be heated A in the transverse
direction (as viewed from front) remains the same in either side in
the leftward and rightward directions. In the event that the bottom
diameter of the article to be heated A is not sufficiently large,
and the infrared incident region 35a cannot be covered when the
article to be heated A is placed with the center of the bottom
surface thereof matched with the center 8e of the second heating
coil 8, the article to be heated A can be placed at the position
where the infrared incident region 35a can be stably covered with
the bottom surface of the article to be heated A, and the distance
from the position of the infrared incident region 35a to that end
of the bottom surface of the article to be heated A in the
transverse direction (as viewed from front) remains the same in
either side in the leftward and rightward directions by moving the
article to be heated A forwardly while watching the infrared
incident region 35a, Also, since the infrared incident region 35a
is provided between the light emitting region 35b and the center 8e
of the second heating coil 8, placement of the article to be heated
A on the heating area 35 so as to cover the light emitting region
35b is effective to assuredly cover the infrared incident region
35a with the article to be heated A.
[0080] Similarly, not only in the case in which the light emitting
region 35b and the infrared incident region 35a are displaced in
the direction forwards and rearwards (in the longitudinal
direction) from the center of the second heating coil 8 and
forwardly, but also in the case where the light emitting region 35b
and the infrared incident region 35a are displaced from the center
8e of the second hearing coil 8, it is preferred that the light
emitting region 35b be arranged at a location radially outwardly of
the center 8e of the second heating coil 8, because the infrared
incident region 35a can be stably covered with the article to be
heated A by covering the light emitting region 35b with the article
to be heated A.
[0081] FIG. 12 illustrates a control circuit for the second heating
coil 8, which can be employed where the sensor unit 48D shown in
FIG. 8 or the sensor unit 48E shown in FIG. 10 is employed. In
addition to the control circuit shown in FIG. 3, an illuminance
detecting means 73 adapted to receive an output from the light
sensor 72 is provided, and the control means 44 is operable to
control an output from the inverter circuit 46 for supplying a high
frequency current to the second heating coil 8 in dependence on an
output from the temperature detecting means 42 and an output from
the illuminance detecting means 73.
[0082] In other words, the light sensor 72 is to detect the
illuminance (or the brightness) of ordinary indoor light, and the
illuminance detecting means 73 is operable in response to an output
signal from the light sensor 72 to compare the illuminance,
detected by the light sensor 72, with a predetermined threshold
value. In the event that the illuminance detected by the light
sensor 72 attains a value higher than a predetermined value, it is
determined that the article to be heated A fails to cover the
infrared incident region 35a, in which case the control means 44
disables a heating control of the second heating coil 8 by the
inverter circuit 46 or suppresses the output of the second heating
coil 8, but in the event that the illuminance detected by the light
sensor 72 attains a value lower than the predetermined value, it is
determined that the article to be heated A covers the infrared
incident region 35a, in which case the control means 44 performs
the heating control of the second heating coil 8 by the inverter
circuit 46.
[0083] Accordingly, the control means 44 performs an output control
of the inverter circuit 46 in response to the output signal from
the infrared sensor 40 only when the illuminance detected by the
light sensor 72 is lower than the predetermined value, thereby to
control the heating output from the second heating coil 8 so that
the temperature or the temperature gradient of the article to be
heated A may be lower than a predetermined value.
[0084] By the construction described above, since the light
emitting region 35b is illuminated in the vicinity of the infrared
incident region 35a, the position of the infrared incident region
35a can easily be noticed and, even when the indoor space is dark,
the infrared incident region 35a can easily be noticed.
[0085] Also, since the light sensor 72 can detect the illuminance
within the indoor space, it is possible to detect that the article
to be heated A is not in position to cover the infrared incident
region 35a, but where the indoor space is dark, it is difficult for
the light sensor 72 to detect that the article to be heated A is
not in position to cover the infrared incident region 35a. However,
since even in such case, the light emitting region 35b can readily
be noticed with eyes due to the light emission, the temperature
control of the article to be heated A by means of the infrared
sensor 40 can be performed stably if the light emitting region 35b
is covered to permit the infrared incident region 35a to be
covered.
[0086] It is to be noted that although the surface area of the
light emitting region 35b is small and, therefore, any displacement
in position between the upper opening 36d, through which light is
projected, and the light emitting portion 35b will be conspicuously
visible, the provision of the light diffusing layer in the light
emitting region 35b in the manner as hereinbefore described can
minimize the visibility of the displacement in position. The
construction in which the light diffusing layer is provided will
now be described with particular reference to FIGS. 13A to 13E.
[0087] The construction shown in FIG. 13A is such that a
semitransparent light diffusing layer 76 is provided over the
entire area of the light emitting region 35b, whereas the
construction shown in each of FIGS. 13B to 13E is such that the
light emitting region 35b is provided with a light diffusing layer
76 mixed together with a site having a higher light transmittance
than that of the light diffusing layer 76.
[0088] To describe further, the structure shown in FIG. 13B is such
that a center area of the light emitting region 35b is rendered to
be a transparent area 78, where no light diffusion layer exists; a
peripheral area is provided in a stripe shape at a location
radially outwardly of this center area and is formed by a
semitransparent annular light diffusing layer 76; and the light
transmittance of the center area is chosen to be higher than that
of the peripheral area.
[0089] Also, the construction shown in FIG. 13C is such that a
plurality of semitransparent round light diffusing layers 76 are
provided in the light emitting region 35b in a scattered fashion
and an area other than the light diffusing layers 76 is rendered to
be a transparent area 78.
[0090] Further, the construction shown in FIG. 13D is such that a
center area of the light emitting region 35b is rendered to be a
transparent area 78 having no light diffusing layer formed therein;
a first peripheral area is provided in a stripe shape at a location
radially outwardly of the center area and is formed by a
semitransparent annular light diffusing layer 76; and a second
peripheral area is provided in a stripe shape at a location
radially outwardly of the first peripheral area and is formed by a
colored light transmittable layer 80 having a light transmittance
lower than that of the first peripheral area.
[0091] Yet, the construction shown in FIG. 13E is such that a
semitransparent light diffusing layer 76 is formed in a grid
pattern in the transparent area 78 provided in the light emitting
region 35b.
[0092] It is to be noted that although in any one of the
constructions shown respectively in FIGS. 13B to 13E, the
transparent area 78 is provided in a part of the light emitting
region 35b, a different light diffusing layer having a light
transmittance higher than that of the light diffusing layer 76 may
be provided in place of this transparent area 78.
INDUSTRIAL APPLICABILITY
[0093] Since the induction heating appliance for cooking according
to the present invention is so designed that the region of
incidence of the infrared rays of light emanating from the article
to be heated such as, for example, a pot upon the infrared sensor
can be easily noticed with eyes, all that is performed by the user
is to place the article to be heated on the top plate so as to
cover the infrared incident region and, hence, the induction
heating appliance for cooking according to the present invention is
useful as an induction heating appliance for home cooking that can
be built in a household kitchen.
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